1. Field of the Invention
This invention relates to a recording head of an ink jet recording device to be used for printer, video output printer, etc. as the terminal for output of copying machine, facsimile, word processor, host computer, a substrate for said head an ink jet recording device, particularly to an ink jet recording head having an electrothermal transducer for generating thermal energy as the energy to be utilized for discharging ink and a functional device for recording formed on or internally of the same substrate, a substrate for said head and an ink jet recording device.
2. Related Background Art
In the prior art, a recording head had a constitution, comprising an array of electrothermal transducers formed on a single crystal silicon substrate, functional devices for driving the electrothermal transducers such as a transistor, a diode array, etc. arranged externally of the silicon substrate as the driving circuit of the electrothermal transducers, with connection between the electrothermal transducers and the functional devices such as transistor array, etc. being done with flexible cable or wire bonding.
For the purpose of simplifying the structure, or reducing defects occurring in the preparation steps, and further improving uniformization of the characteristics of the respective devices and reproduction of high quality head preparation, etc., there has been known an ink jet recording head having electrothermal transducers and functional devices provided on or internally of the same substrate as proposed in Japanese Laid-open Patent Application No. 57-72867.
FIG. 12 is a schematic sectional view showing a part of the recording head having the construction as described above. Numeral 901 is a semiconductor substrate comprising a single crystal silicon. Numeral 902 is the collector region of an N-type semiconductor, 903 the ohmic contact region of an N-type semiconductor with a high impurity concentration, 904 the base region of a P-type semiconductor, 905 the emitter region of an N-type semiconductor with a high impurity concentration, and the bipolar transistor Numeral 920 is formed of these. 906 is a silicon oxide layer as the heat accumulation layer and the insulating layer, 907 a hafnium boride (HfB.sub.2) as the heat-generating resistor layer, 908 an aluminum (Al) electrode, 909 a silicon oxide layer as the protective layer, and the recording head substrate 930 is constituted of all the members as mentioned above. Here, 940 becomes the heat generating portion. The ceiling plate 910 is bonded to 930, and sectionalizes the liquid channel communicated to the discharge opening 950A in co-operative fashion.
The substrate for recording head with such constitution (heater board) is connected to functional device arrays such as the array of the heat generating portion (heater) 940 and the array of diodes or transistors for driving this through the matrix wiring portion arranged between these. However, in the constitution of the prior art, because the matrix portion and the functional device portion are arranged at the sites separated on the heater board, the following problems have been involved.
i) The size of the heater board cannot be made small without accompaniment of performance deterioration.
ii) Segment electrodes for driving selectively the heater are located outside of the width of the heater row, whereby the heater board size is larger corresponding thereto, and further continuous arrangement is also impossible.
iii) Wiring resistance is large.
iv) Since the distance from the heater to the functional devices for driving is not uniform, the resistance value correction is difficult.
Also, since many wirings have been applied in the same layer (e.g. the second layer) as the heater layer, there have been such problems as follows:
i) the second layer wiring cannot be made thick because the wiring resistance is made small by the influence of the protective layer of the heater;
ii) the second layer comprises a double structure of both the heater material and the wiring material, and therefore if the second layer portion is much, the yield of bridges, etc. is poor. Further, there has been the problem that high precision is required for the film thickness of the respective layers, because the resistance value correction of the second layer wiring is done in the first layer.
The substrate for recording head with such constitution (heater board) is connected to an array of the heat-generating portions (heater) 940 and an array of functional devices such as an array of diodes or transistors through a matrix wiring portion arranged between these. The functional device array portion is arranged on the heater board gradually departed as the first row, the second row, . . . the nth row from the heater portion.
Therefore, since the distance between the heater portion and the functional device array portion is different for each row, the normal direction voltage of the functional device such as diode or transistor tends to be larger as remote from the heater portion (the substrate temperature becomes lower) depending on the temperature distribution of the heater board, particularly involving the problem that its variance is greater as the temperature of the heater board becomes higher in printing for a long time, etc. to have deleterious effect on printing quality.